Is there any particular reason why we can only have one guide layer?

People may remember my campaign for nested layers because I tend to have one Xara file and use it to hold all my assets and designs in one place, rather than separate files.

Today I was using the guides layer to lay out a card sheet. Once I've done that I'd like to lay out a web design in the same document, so if I want to use guides again I need to delete the card layout guides or just put up with them.

I entirely understand that I can make my own 'guides' by drawing in a layer above my proposed artwork and make it uneditable.

So why only one guide layer? Multiple guides would be good, even with the layers as they are (even better with nested layers).

Paul